1. Field of the Invention
The present invention relates to an image forming apparatus operable in plural operation modes, and more particularly, to an image forming apparatus operable in plural operation modes such as an electrophotographic copying machine comprising plural operation modes such as analogue and digital copying modes.
2. Description of Related Art
Conventionally, in electrophotographic copying machines, there have been put into practical use an analogue copying machine for forming a latent image on a photoconductor and developing the latent image into a visible toner image so as to print a so-called analogue image on a sheet of copying paper, and a digital copying machine for printing dot images or so-called digital image on a sheet of copying paper according to digital image data. Further, a copying machine of composite function type comprising an analogue copying system and a digital copying system is proposed, for example, in the Japanese patent laid open publication (JP-A) No. 55-123270/1980.
In the copying machine of composite function type, the analogue and digital copying systems utilize a common electrophotographic printing section. However, the analogue copying system utilizes an exposure optical system for projecting light reflected from a document onto a photoconductor. On the other hand, the digital copying system utilizes an image read section using a CCD image sensor or the like, and an image write section such as laser printer or the like. Either the analogue copying system or the digital copying system of the copying machine of composite function type can be used depending on the use so as to make the best use of the features of each copying system. For example, when a copy which has been produced by the digital copying system is recopied, degradation in the quality of the image can be reduced by reproducing the copy using the analogue copying system. Furthermore, an analogue half tone image and a digital binary image can be composed by the copying machine of composite function type.
However, since the copying machine of composite function type has many functions, it is difficult to set the operation conditions such as selection of developing units in each operation mode. Therefore, there is caused such a problem that the copying machine of composite function type can not operate in the operation mode if operation conditions set by the operator do not conform to operation conditions which are inhibited or are not permitted therein.